Thinking this through:
Ultimately, the logic is that the buyer won't make a purchase/no purchase decision due to set-times (late-shows/early-shows excluded) because set-times were typically not announced until the day of the show. Us show-goers, and the younger folks that replace us over time, are going to purchase tickets to shows that they want to see, and if no set-time is ever posted, we/and those that follow us, are just going to show up on time to try to make sure that we/they see the part of the show we want to see.
So giving us notice of the set-times is something that IMP/930 does for us that is nice for it to do, but it is not really necessary or a "whether to buy a ticket" decision point for us. And it may make IMP/930 slightly more money if we are in the club longer, and makes the openers happier that there is a larger crowd present (though, does anyone really care about making the openers happy?)
The thing is that IMP/930 does nice things for us that it doesn't need to do (formerly posting set-times), FWB, World's fair, some presales, this BBS, and the like, that it doesn't have to do, and because of that it is hard to understand why IMP/930 would stop doing a nice thing for us that it didn't ever need to do and it causes this dissonance.
Or